I love the Fleischer Superman cartoons. The animation is smooth and fluid with vivid colors. The distinct art-deco style, vintage science fiction imagery, and use of noirish shadows gave them a look unlike any other cartoons. The music and voice work is superb. They're fun, accessible, enduring animation classics.
The seventh in the series is one of the best and most interesting. A Native American scientist demands the return of Manhattan to his people. Everybody but Lois Lane believes his threats to be empty. Lois sneaks onto the guy's motorboat and follows him back to his secret lair, which is a very cool underwater laboratory. After the scientist straps Lois into a chair ready-made to keep someone prisoner, he begins to unleash his earthquake device on the city. He has large electric cables connected to the bedrock of Manhattan island and, when he sends electric surges through the cables, he causes earthquakes. This results in some exciting scenes. Superman is quickly on the job and into the water, where he discovers the cables and proceeds to try to undo them. This proves harder than it looks. The rest of the cartoon is fun, non-stop action as Supes tries to save the city from the earthquake machine.
This is a great cartoon. The plot is a little more detailed than the average entry in the series and the villain is very unique. It's also interesting that the city is explicitly referred to as the real place of Manhattan, as opposed to the fictional city of Metropolis where Superman's adventures usually take place.
